Apparatus for trimming a flanged end of a tubular article

ABSTRACT

A punch and die assembly for trimming the flared end of a can body comprises a reciprocable punch (10), and a split die (15) consisting of two semi-circular segments (14, 16) movable between an open position allowing infeed of article (A), and a closed position around the article. During co-operation of the cutting edges (35, 61) and (51, 62) on the punch (10) and die (15) respectively to trim the can body, the punch is centralized accurately in relation to the die by engagement of a radially outwardly facing surface (521, 74) on the die with a radially inwardly facing surface (321, 73) on the punch; rough alignment between punch and die having previously been achieved by engagement of further surfaces on the punch and die when the die was closed.

The present invention relates generally to apparatus for trimming aflanged end of a tubular article and has particular, but not exclusive,application for trimming a flanged end of a plastics body for a food orbeverage container, prior to double-seaming the flanged end to a metalend closure.

In order reliably to make an effective leak-proof double seam betweenthe flanged end of a container body and an end closure, the flanged endmust be provided with an accurately trimmed edge. Conventionally, thenecessary degree of accuracy has been achieved by mounting a punch forvertical movement on the pillars of a standard pillar and die set. Thepunch is mounted on an upper beam which is reciprocated along two ormore pillars toward and away from the die beneath it. To achieve theaccurate alignment required between the punch and the die, a massiveframework including the pillars is required to achieve sufficientrigidity for accurate alignment to be possible. However, thesetraditional pillar and die sets are extremely expensive; they aremassive and access for the article is often restricted. One object ofthe present invention is to enable the required degree of accuracy to beprovided for a flange trimming operation on a plastics container bodywithout the need for the massive structure of the pillar and die setswhich have been used hitherto.

For a tube having a flanged end to be correctly positioned in an annulardie which must necessarily have a smaller internal diameter than theuntrimmed flange, one of two conditions must be provided. Either theremust be sufficient space provided in the apparatus for the tube to befed axially into the die until the flange reaches the die, or the diemust be formed in segments which are separable and movable between aclosed position in which the die is formed, and an open position inwhich the segments are spaced from one another. The invention relates toapparatus of the second type.

Accordingly, the present invention provides apparatus for trimming aflanged end of a tubular article, comprising a punch and a die, thepunch and the die being relatively movable along the axis of the articleand on such relative movement cooperating to sever and thereby trim theflanged end of the article at a required diameter; the die being formedof a plurality of segments which are movable between a closed positionin which the die is formed and an open position in which the segmentsare spaced from one another, and the apparatus including aligning meansfor the punch and die comprising a radially outwardly facing surface onthe die and a radially inwardly facing surface carried by the punch, thetwo surfaces being brought into engagement by relative axial movement ofthe punch and die towards one another so as to hold the segments of thedie securely together and retain the punch and die in correct alignmentat least while the flanged end is being trimmed.

An advantageous feature of the split die arrangement of the describedembodiments is the provision of further surfaces which are mutuallyengageable to provide a lateral alignment of the punch and die which isin addition to the alignment provided by the first-mentioned surfaceswhen the punch is operated. The further surfaces are brought intoengagement when the die segments are moved from their open to theirclosed position and so provide a rough or initial alignment of the punchand die which is in advance of the alignment provided by thefirst-mentioned surfaces.

In accordance with one embodiment of the invention, the die segments areattached to respective pivotally mounted members so as to follow anarcuate path in moving between their open and closed positions, the saidfurther surface of the die being provided by the said pivotally mountedmembers.

In a second embodiment, the die segments may be arranged to follow alinear path in moving between their open and closed positions.

In either case, the punch or the die may have an associated surfacearranged to engage the article and to hold and locate the same for thesaid trimming operation.

Embodiments of the invention are described below, with reference to theaccompanying drawings, in which:

FIG. 1 illustrates apparatus according to the invention viewed fromabove and partially in horizontal section, with the die segments open atthe start of a trimming operation of one end of a container body;

FIG. 2 illustrates the apparatus of FIG. 1, with the die segments closedaround the container body to be trimmed;

FIG. 3 shows an end elevation of the apparatus of FIGS. 1 and 2;

FIGS. 4 and 5 illustrate, on an enlarged scale, stages of the trimmingoperation, subsequent to the stages shown in FIGS. 1 and 2; and

FIG. 6 illustrates an alternative embodiment of the apparatus shown insection and with opposite sides of the apparatus shown in differentpositions of operation;

FIG. 6a is an enlarged illustration of the circular portion of FIG. 6;and

FIG. 7 is an end view of the apparatus of FIG. 6 additionally showingthe mechanism for closing the die.

Referring to FIGS. 1 to 3 of the drawings, the apparatus is shown inrelation to a article A in the form of a container body of polyethyleneterephthalate (PET) having at least one end (as shown) necked-in andoutwardly flared. The apparatus generally comprises a punch 10, and asplit die assembly 12 having two identical half segments 14,16, of anannular die 15.

The punch 10 is mounted for reciprocal motion along its axis and issupported, via a cylindrical bearing sleeve 18, in a yoke 20 rigidlymounted on a base plate 22. The punch is reciprocated in anyconventional manner by drive means which are not shown in the drawingsbut which could comprise, for example, an eccentric or a cam, or apneumatically or hydraulically powered piston. The drive means act on adrive rod 24.

The punch 10 comprises a cylindrical shaft 26 which has an accuratelymachined surface which serves as the bearing surface not only for thebearing sleeve 18 but also for a further bearing member which will bedescribed hereinbelow. Integral with the shaft 26 is an enlargeddiameter portion 28 of the punch, to which a head 30 for the punch isreleasably secured by means of a bolt 31. The punch head 30 is generallydisc-shaped and has it leading face formed with a flat-bottomed annularchannel 33 within a peripheral wall 32 which has a radially inwardlyfacing cylindrical surface 321. The channel 33 surrounds a central boss34 of the punch head, the outer edge 35 of this boss providing thecutting edge 35 of the punch 10. Projecting axially of the punch head,out of its channel 33, is a plurality of outwardly biassed scrap-releasepins 36. In a modification, the pins are replaced by a continuousannular scrap-release ring (not shown).

The die segments 14,16 are individually mounted for swinging movement ina horizontal plane about respective vertical shafts 37 which are mountedin the yoke 20. The die segments 14,16 can be swung between an openposition (FIG. 1) and a closed position (FIG. 2) and are driven, viapiston rods 38, by pneumatic or hydraulic cylinders 40.

Each die segment is releasably mounted on a respective generallysemi-cylindrical half portion 42 of a cylindrical body member 43 viabolts 44. It is comprised of a semi-circular half portion 46 of an endplate 47 and, releasably supported on the end plate portion 46 via bolts48, a semi-circular portion 49 of a collecting ring 50. The collectingring 50, formed by the two portions 49 when the die segments are intheir closed position (see FIGS. 2 and 4), provides the cutting edge 51of the die, for cutting co-operation with the cutting edge 35 of thepunch. In addition, the collecting ring is formed with a collectingridge 52 which provides a radially outwardly facing cylindrical surface521.

The operation of the apparatus will now be described:

The apparatus is initially as shown in FIG. 1, with the die segments14,16 in their open position and a article A having a flared endpositioned between them. The article, suitably supported, is located inposition by a cradle 53 (FIG. 2), and is inserted by the cradlesufficiently far into the apparatus so that the die segments can closearound the flared end of the article.

In the second step of the operation, the die segments 14,16 are closedaround the article A, moving into the position shown in FIG. 2. In thisposition, the die segments contact one another at their free ends toform a full annulus, the end plate 47 formed of the portions 46 thenmaking contact with the cylindrical wall of the article A at acylindrical inner face 54 so as to hold and laterally align the articleready for trimming. It will be seen that the engagement of the articleby the face 54 occurs immediately beneath the neck of the article, andso is optimally effective for aligning the article for the trimmingoperation.

In the closed position of the die assembly, illustrated in FIG. 2, aninternal cylindrical surface 56 formed adjacent that end of the bodymember 43 remote from the die 15 makes contact with the surface of theshaft 26 of the punch 10 behind the enlarged portion 28 and head 30 ofthe punch. By means of this contact, there is an initial alignment madebetween the punch 10 and the die assembly 12 prior to the operation ofthe punch. The body member 43 accordingly forms the second bearingmember with which the shaft 26 co-operates, as mentioned above.

The next stage of the operation is to advance the punch 10 and therebymove the cutting edge 35 of the punch head 30 towards the cutting edge51 on the collecting ring 50 of the die. However, before the cuttingedges 35 and 51 can act on the article to sever the same, an alignmentmeans between the punch head 30 and die 15 becomes operational. Thisalignment means comprises the engagement of the surface 321 on the wall32 of the punch head 30 with the surface 521 on the ridge 52 on thecollecting ring 50 of the die. The punch is advanced until it reachesthe position shown in FIG. 4 where the wall 32 is collected by the ridge52, that is to say, the surfaces 321 and 521 are engaged and thereafterconstrained to slide over one another after any necessary lateralcentralising movement of the punch 10 and die assembly 12 in relation toone another; by this means, the punch and die are further aligned to ahigher degree of accuracy, the initial alignment having been made bycontact between the cylindrical surfaces 56 and 26 as described above.It is to be noted that this alignment means is located in the immediateneighbourhood of the cut and formed by surfaces which are immovable inrelation to the respective cutting edges 35,51 because they are carriedintegrally and in common by the collecting ring 50; the alignment meansis therefore optimally effective to achieve accurate alignment of thecutting edges 35,51 in relation to one another.

A further function of the engagement of the ridge 52 on the die by thewall 32 of the punch is to hold the segments of the die securelytogether whilst severance is taking place. The die is thereby preventedfrom being expanded radially by any hoop stresses imposed on it.

With accurate alignment achieved, the punch 10 is then further advancedtowards the article A, the cutting edges 51 and 35 effecting an accuratetrim on the flanged end region of the article. To ensure a completetrim, the punch head 30 is advanced beyond the cutting edge 51 on thecollecting ring 50 into the position shown in FIG. 5, the over-travelinvolved being of the order of 2 mm. The punch 10 is then retracted and,during retraction, the spring-biassed scrap-removal pins 36 push awayany scrap which may be adhering to the punch, the scrap being allowed tofall by gravity clear of the apparatus when the die assembly 12 opens.The article is finally removed from the apparatus.

FIGS. 6, 6a and 7 show an alternative embodiment in which the diesegments 14 and 16 move along a linear radial path between their openand closed positions. The punch 10 is, as before, supported on acylindrical shaft 26 which is axially reciprocated by means not shown.The punch head 30 is bolted to the shaft 26 and has mounted thereon acutting ring 60 contoured in accordance with the radially inner portionof the flanged end of the article to be trimmed and providing a cuttingedge 61 which co-operates with a cutting edge 62 on the die to sever theflange of the article A. The two segments 14, 16 of the die are urgedradially along guide bars 63 into their closed, die forming position, bymeans of cams 64 and against the action of springs 65. The surfaces ofthe cams bear on rollers 66 carried by the die segments.

A clamping ring 67 is mounted to slide on the shaft 26 and is urgedtowards the punch head 30 by means of a spring 68; the shaft 26 beingjournalled within a fixed housing 69 by means of bearings 70. Theclamping ring 67 is provided with an annular extension 71 which engagesin a corresponding groove 72 formed in the segments 14, 16 when the dieis closed and the punch is advanced. By means of a radially inwardlyfacing frustoconical surface 73 on the extension 71 and a radiallyoutwardly facing frustoconical surface 74 on the groove 72, the clampingring holds the segments of the die securely together and retains thepunch and die in correct alignment while the flanged end of the articleA is being trimmed.

A flange support and ejection ring 75 is mounted for sliding movement onthe punch head 30 under the action of a spring 76 and serves to supportthe radially outer portion of the flanged end of the article during thetrimming operation. The cutting edges 61 and 62 co-operate to sever, andthus trim the flanged end at a required diameter which defines theradially inner and outer portions thereof.

The operation of this apparatus is as follows. With the die in its openposition and with the punch retracted as shown on the right hand side ofFIG. 6, the article is positioned axially in line with the punch. Thepunch is then advanced so that the punch head, and more particularly thecutting ring 60, locates in the open flanged end of the article. Intimed relation, the two segments of the die are brought together underthe action of the cams 64 until an internal cylindrical surface 80 onthe die segments comes into sliding contact with an external cylindricalsurface 81 on the punch head at the same time as the die segments comeinto contact with one another. At this stage there is an axial clearancebetween the clamping ring 67 and the die segments, but subsequentcontined advance of the punch causes the annular extension 71 of theclamping ring to engage in the groove 72 on the die as explaned above.This position is shown in the left in FIG. 6.

Continued advance of the punch beyond the position shown on the left inFIG. 6 causes severance of the flanged end between the cutting edges 61and 62 followed by rearward movement of the trimmed portion of theflanged end against spring 76 whilst held between the die segments andthe support and ejection ring 75.

After the clamping ring 67 has fully engaged the die segments by meansof extension 71 and groove 72, further advance of the punch causes thering 67 to slip along the shaft 26 against the action of spring 68. Thusthe die segments are held firmly together by the clamping ring 67 whilethe flanged end is being trimmed. After the two cutting edges 61 and 62have passed one another sufficiently to ensure severance, the punch isretracted and the die segments are moved to their open position allowingthe trimmed portion of the flanged end to be ejected from off thecutting ring 60 by the ring 75 and to drop out of the apparatus.

It should be noticed that the cutting edge 62 is provided on a cuttingring 82 which is formed in two segments and is replaceably mounted onthe die. The cutting rings 60 and 82 can each be easily replaced whenworn or damaged.

It will also be appreciated that the clamping ring 67 engages the shaft26 over a substantial area and is thus accurately aligned coaxiallytherewith even though it can slide axially along the shaft.

Although the embodiments of FIGS. 1-5 and FIGS. 6 and 7 have beendescribed in relation to dies movable along arcuate and linear pathsrespectively it will be appreciated that these and other details ofconstruction could be interchangeably applied.

Various modifications of the apparatus as particularly described arepossible. For instance, the split die could comprise more than twosegments.

The various advantages of the apparatus described include its relativesimplicity in providing accurate trimming without the need for a massiveconstruction. Furthermore, the only components which are required to bemachined to a high degree of accuracy are those which determine thefinal accuracy of alignment between the die and punch, and therefore ofthe cut which is achieved. These components are arranged to be readilyreplaceable either if they should become worn, or where a cut of greateror lesser diameter is required.

It will be understood that the described apparatus could be adapted tocarry out trims on non-circular articles, such as those of oval orpolygonal cross-section. In addition, it could be adapted for cuttingplastics, metal, or other materials, the components being suited to thematerial involved.

We claim:
 1. Apparatus for trimming a flanged end of a tubular article,comprising a punch and a die, the punch and the die being relativelymovable along the axis of the article and on such relative movementcooperating to sever and thereby trim said flanged end of the article ata required diameter; the die being formed of a plurality of segmentswhich are movable between a closed position in which the die is formedin surrounding relation with the article and an open position in whichthe segments are spaced from one another, and the apparatus includingaligning means for the punch and die comprising a radially outwardlyfacing surface on the die and a radially inwardly facing surface carriedby the punch, the radially outwardly facing surface on the die and theradially inwardly facing surface carried by the punch being brought intoengagement by relative axial movement of the punch and die towards oneanother so as to urge the segments of the die radially inwardly intomutual die-forming relationship and furthermore retain the punch and diein correct alignment at least while the flanged end is being trimmed. 2.Apparatus according to claim 1, which includes further surfaces on thepunch and the die which are mutually engageable to provide furtherrelative lateral alignment of the punch and die, the further surfacesbeing brought into engagement when the die segments are moved from theiropen to their closed position.
 3. Apparatus according to claim 1,wherein the die segments are attached to respective pivotally mountedmembers so as to follow an arcuate path in moving between their open andclosed positions.
 4. Apparatus according to claim 1, in which the diesegments are mounted to follow a linear radial path in moving betweentheir open and closed positions.
 5. Apparatus according to claim 4, inwhich the die segments are moved towards their closed position by camsdriven in timed relation to the punch.
 6. Apparatus according to claim1, wherein the die has an associated surface arranged so as, when thedie segments are moved to their closed position, to engage the articleexternally and to hold and locate the same in relation to the die forthe said severance operation.
 7. Apparatus according to claim 1, whereinthe punch has an associated surface arranged to engage the articleinternally and to hold and to locate the article in relation to thepunch for the said severance operation.
 8. Apparatus according to claim1, in which the radially inwardly facing surface carried by the punch isprovided on a clamping ring mounted for sliding movement on the shaft ofthe punch.
 9. Apparatus according to claim 1, wherein the radiallyoutwardly facing surface on the die is provided by an annular grooveformed in the die.